FIG. 1 depicts a portion of a conventional magnetic transducer 10, such as a conventional read transducer or other device. The conventional transducer 10 resides on a conventional substrate 11, such as an AlTec substrate. The conventional transducer 10 includes a conventional bottom shield 12, conventional shield 12, conventional antiferromagnetic (AFM) layer 18, conventional sensor 20, and conventional top shield 40. The transducer 10 also typically includes seed layer(s) (not shown) between the conventional AFM layer 14 and the conventional shield 12. The conventional shields 12 and 30 typically include NiFe and are formed by plating.
The conventional sensor 20 typically includes an antiferromagnetic layer 14, a pinned layer that is usually a synthetic antiferromagnetic (SAF) layer 22, a nonmagnetic layer 24, a free layer 30, and a capping layer 26. The conventional SAF layer 22 typically includes two ferromagnetic layers (not separately shown) separated by a nonmagnetic spacer layer (not shown). The ferromagnetic layers are generally antiferromagnetically coupled. The magnetization(s) of the conventional SAF layer 22 are pinned by the conventional AFM layer 14. More specifically, the first ferromagnetic layer adjoining the conventional AFM layer 14 has its magnetization pinned by the conventional AFM, for example via exchange interaction. The remaining ferromagnetic layer has its magnetization pinned because it is strongly magnetically coupled with the first ferromagnetic layer. The conventional nonmagnetic layer 24 may be a barrier layer or a conductive spacer layer. If a barrier layer 24 is used, then the sensor 20 is a tunneling magnetoresistive (TMR) sensor. If a conductive spacer layer 24 is used, then the sensor 20 is a spin valve or for current perpendicular to the plane giant magnetoresistance sensor.
The conventional free layer 30 includes a CoFe layer 32, a CoFeB layer 34, a conventional nonmagnetic Ta layer 36, and a conventional NiFe layer 38. The conventional free layer 30 has a thin CoFeB layer 34, which has high spin polarization. As deposited, the CoFeB layer 34 is amorphous. The second magnetic layer is a conventional NiFe layer 38. The conventional NiFe layer 38 typically has less than ten percent Fe and prefers an fcc crystal structure after annealing. The conventional free layer 30 also uses a conventional non-magnetic Ta layer 36 to separate the layers 34 and 38. This separation allows a higher high Q-factor, or high magnetoresistance at low RA.
Although the conventional transducer 10 and conventional sensor 20 may function, issues may arise in higher density magnetic recording applications. The areal storage density in a hard disk drive using the conventional transducer 10 increases dramatically every year. In order to maintain the magnetic properties of the transducer 10, the shield-to-shield distance, h1, is desired to be decreased. This decrease may require thinner sensors 20. Further, a high ΔR/R (magnetoresistance) and low RA, or high Q factor, are desired. The conventional transducer 10 is also desired to be magnetically soft. In addition, low noise and a near zero magnetostriction is also desired. However, various features of the conventional sensor 20 and other conventional layers 14 and 26 contribute to a larger shield-to-shield spacing h1, as well as other issues with the conventional sensor 20.
For example, the conventional free layer 30 is typically thick. The higher thickness is used to achieve higher magnetoresistance and lower magnetostriction for the conventional free layer 30. The conventional NiFe layer 38 of the conventional free layer 30 may have a higher damping constant and lower moment. The magnetic noise for the conventional transducer 10 is proportional to damping constant α and inversely proportional to saturated magnetization Ms of the free layer 30. Thus, the NiFe layer 38 may contribute additional magnetic noise. The NiFe layer 38 may also be thicker to achieve the desired magnetostriction and higher total moment of the conventional free layer 30. Similarly, though functional, the conventional Ta layer 36 may cause a magnetic dead layer that may result in a higher damping constant. Further, all of the layers 32, 34, 36, and 38 contribute to the large thickness of the conventional free layer 30. Thus, a thicker conventional free layer 30 is used to obtain the desired performance, but increases the shield-to-shield spacing.
Other layers are also made thicker to achieve the desired performance. The reduction of the thickness of various layers, such as the conventional AFM layer 14 or conventional seed layers (not shown) may adversely affect performance of these layers. For example, reducing the thickness of the conventional AFM layer 14 may reduce its ability to pin the magnetizations of the conventional SAF 22. This may allow the magnetizations of the conventional SAF 22 to change direction, at least to a degree. Consequently performance of the conventional transducer 10 is adversely affected. Similarly, a reduction in the thicknesses of the conventional seed layers (not shown) may reduce the quality of the conventional AFM layer 14. As a result, the ability of the conventional AFM layer 14 to pin the magnetization of the conventional SAF 22 is again diminished. Consequently, performance of the conventional magnetic transducer 10 may again be adversely impacted by simply reducing the thickness of various layers.
Accordingly, what is needed is a system and method for providing a transducer that may be usable for higher density recording.